Electric fuse



May 8, 1934.

F. c. LA MAR 1,958,366

ELECTRIC FUSE Filed Oct. 16. 1931 II ll INVENTOR PatentedrMay 8, 1934 .Y

UNITED STATES PATENT OFFlCE ELECTRIC FUSE Frank C. La Mar, New York, N. Y., assignor to Great Western Fuse Company, New York, N. Y., a corporation of Delaware Application October 16, 1931, Serial No. 569,183

1 Claim. (Cl. 200-119) This invention relates to electrical devices, esconsists generally of a tubular shell 1, formed of pecially to electrical devices for interrupting an insulating material; knife blades 2 and 2 formed, electric circuit upon an abnormal ow of current preferably of copper, one extending outwardly therein, and more particularly to such a device from each end of the member l; and a renewable Y 5 including an easily fusible link, commonly known fusible link 3, formed of metal, connecting the 50 as a fuse. tangs of the knife blade terminals 2 and 2.

A principal object of applicants invention is Various constructions have been devised for to provide a device of the type specified of such supporting the knife blade terminals, as 2, in asconstruction that the easily fusible link therein sociation with the tubular casing 1, and for closv 10V may oe replaced, after being fused by an abnormal ing the ends of the casing so that flames and hot flow of current, by a fresh link, without the use of gases generated by the fusion of the fusible link any tools whatsoever. 3, by an abnormal flow of current, may be prop- A further object of the invention is provide a erly directed and cooled.

fuse of the type specified which not only may be In the arrangement shown in the drawing, the v A15 assembled without the use of tools but'which will knife blades are supported and associated with preferably be so constructed that a fuse link may the tubular casing 1 by a substantially convennot be replaced by a fresh link of a higher curtional arrangement. Each end of the tubular rent carrying capacity. casing 1 has a metallic ferrule thereon, as 4 and @ther objects and advantages will appear as the 4. Each knife blade, as 2, has rigidly attached "20 description of the particular physical embodithereto a shoulder member, as 5 and 5. This ments selected to illustrate the invention proshoulder member 5, as best shown in Fig. 4, is in gresses, and the novel features of the invention the form, substantially, of a disc, or washer, just will be particularly pointed out in the appended fitting within the bore of a ferrule, as 4, somewhat claim. flattened at diametrically opposite points, as at 6. k

In describing the invention in detail and the Above the shoulder 5 there is a slotted washer, as particular physical embodiments selected to illus- 7 and 7 on each knife blade. Each of these slottrate the invention reference will be had to the ted washers has spaced prctuberances 3 spacing accompanying drawing and the several views the washers, as 7, siightly from the end of a ferthereon in which like characters of reference rule, as 4.

designate corresponding parts throughout, and Aninternal threaded cap, as9 and 9 cooperates in which: with each ferrule, as 4. Each cap has a fiange, Figure 1 is a longitudinal sectional view of a as 10, which cooperates with the slctted washer, renewable cartridge fuse of the knife blade type; as "I, for forcing that washer against the shoulder pig. 2 is a icngitudinal sectional View of the de- 5 with its protuberances 8 in contact with the end y 5 vice, as shown in Fig. 1, but taken on a plane at of a ferrule, as 4. CO

a iight angle to the plane upon which the section The insulating spacing, or bridge bar 11, ex- ShOWl by Fg- 1 is taken; Fig. 3 is a fragmentary tends from one tang end 22 to the other 23. This longitudinal sectional view on the plane indicatspacing bar 11 is attached to the tang of each of ed by the line III-111 cf Fig. 1, viewed in the dithe knife blades, as 2. This is done, preferably, A rection of the arrows at the ends of the line; Fig. by providing metal saddles, as 12 and 12. These 4 is a cross-sectional view of the device, as shown saddles are best made substantially U shaped, as by Fig. 1, taken on the plane indicated by the line is best shown in Fig. 5. The saddles, as 12', are ITL-IV, viewed in the direction of the arrows at attached, together with the proximate end of a the ends of the line; Fig. 5 is a cross-sectional View bridge bar 11, to the adjacent knife blade tang of the device, as shown by Fig. 1, taken on the 23 by any suitable appropriate means. It is pre- Eil-0 71355 In order to illustrate the nVentOrl, a well saddles as 12 and so holds the tang, the metal sadplane indicated by the line V-V of' Fig. 1, viewed ferred to use a fiat headed screw, as 13, threaded in the direction of the arrows at the ends of the into the tang end of the knife blade. This flat line; Fig. 6 is a cross-sectional view correspondheaded screw 13 passes through the end of the ing to Fig. 5, but illustrating a modified form. insulating bridge piece 11 and through the metal known form of knife blade cartridge type renewdie and the end of the bar rmly together. able fuse has been selected. Heretofore, the fusible link 3 has been attached, The form of knife blade cartridge type renewat its ends, to the tang of a knife blade by placable fuse selected for illustration and shown in ing it under a washer, which washer is pressed the drawing is substantially conventional and upon by the head of a machine screw which is 110 threaded into the tang of the knife blade. This screw was manipulated by means'of an ordinary screw driver. This form of connection has its objections.k It is necessary that a screw driver or similar tool be used in order to replace a burned out fuse link. Further, in the ordinary construction, if this link corresponding vto 3, burns out, itmay be replaced by afuse link of greater carrying capacity or by a plurality of fuse links of thesame carrying capacit Y In order to avoid the disadvantage arising from` the necessary use of a screw driver or similar tool, applicant provides a constructionlwhich may be manipulated without the use of. anyvtools.

A washer l4is provided against which bears the -head 15 of a screw 152 screw'threa'ded'into the.

tang 23. This screw 152 is manipulated, to tighten or loosen, by a member ixedly attached .thereto which affords a'manually operable extension. In the preferred form, a lever, as 17', is xedly attached in any appropriate .manner to the end of the screw opposite the headr The arm 17 affords a means bywhich the screw 152 may be. turned so as todcause the head 15, to move away from or toward the tang 123 so that the slotted end 3 of the fuse link lmay be slipped under thev Washer 14 and partially around the screw 152, and then by manipulating the arm 17', thehead l5' will force the washer Vlet against the endof the link 3 into Vtight engagementwith the tang 23.

In orderto prevent a link lof increased carrying capacity. being put in place after the proper carrying capacity link has been fused, applicant provides that the head 15' can be moved .only such a-distancefromthe tang 23 that only a link of proper rcarrying capacity, that is, a link of proper thickness can be positionedbe'tween the washer 14V and the tang 23. In orderto effectuate. this Ylimited movement of the screw 152, applicant pre- Vfers to arrange the arm 17 in such a manner that it canonly move through a limited arc, that is, its movement is restricted by a stop interposed in its path. It is preferable to use the underside of a shoulder, as 5', as the stop.V In such'case the arm as 1'?, as shown inlFig; 3, when turned to the dotted line position has moved the limit and the head lhas been moved as far from the tang 22 as it may be moved. Y

Y Instead of using an arm such as 17 which contacts with a stop to limit its movement, Imay vusera thumb terminal 18, as shown in Fig.A 6.

' This thumb` terminal is of suchasize .that it may turn completely around.Y It is, however, rigidlyV attached to the screw V152. Upon turning the thumb terminal 18 the limit of its movement ofthe bridge 11 thereby limiting its movement.

YThe amountlwhich the thumb terminal 18 may move or rotate may be madesuchthat a proper thickness only of link 3 may be positioned under .the washer 14 or the terminal 18 may be so positioned with regard to the bar 11 that it will not vcontactwith the bar lluntil the head 15' of the screw 152 has been moved such a distance that two or more 4fuse'links vmay be placed under the From the hereinbefore given description it will Abe seen thatrapplicantfhas provided a knife blade cartridge type renewable fuse which may be assembled and disassembled without the use of` any tools whatsoeverythat the fusible link-maybeY assembled or replaced withoutrthe useof any tool; and a construction is provided whereby a fusible link of proper carrying capacity only can be inserted in the fuse.

It is to be understood that applicant by illustrating and describinga knife blade fuse does not intend to excludethevuse of his Vnew construction in connection with what are knownras ferrule type fuseswhich have no knife bladesr vAlthough applicant hasparticularly described one particular physical embodimentof his invention and explained the principle andmode of operation thereof, nevertheless, he desires to haveV it understoodthat the Vform selected is merely illustrative butV does Y not exhaust *the Y possible physical` embodiments .of theidea` of means underlying the invention.V

.WhatI claim -as newand desire to secure by Letters Patent of theLUnite'd States, is:

Y In a renewable v*knife blade, cartridge fuse two spaced` kknife blade tangs each rformed with a screw ,threaded orifice therein; a'screw threaded bolt positioned in the screw threaded orifice, said bolt being-formed with an enlarged head amanuallyVV operable arm xedly attached to the other end of said bolt;and means for limiting the ro-` tation of saidV bolt whereby the separation of the headthereof from the tang is limited so that only a fuse link not above the proper carrying capacity may be inserted Vbetween the headof said bolt Y FRANK C. LA MAR. 

